First the good news! Shredded Storage works like a charm on SQL Server 2008 R2 SP1. I had a 7GB content db with an average of 2 versions per document (scanned pdf), which shrank right down to 4GB after being migrated to SP 2013. Yay!
Now the bad news...
SharePoint Storage Metrics and Site Quotas do not take this into consideration at all. They still count each version as a unique copy and when adding up the total tally they will give you a number multiple times greater than what is actually being used on disk. Although this is not necessarily a huge issue, it does make "managing by quota" a much harder task as the difference between the quota and the actual space used will get bigger and bigger as time progresses.
So be warned! When you site collection complains at you for maxing out on your pre-configured 50GB storage limit, don't go panicking about your DB space right away. Good chance you're still sitting happily below your warning level with tens of gigs to spare on disk.